//
// Created by lenovo on 2023/12/25.
//
#include<bits/stdc++.h>
using namespace std;
#if 0
#define pi 3.14159
int main()
{
      double  r = 0;
      cin >> r;
      printf(" A=%.4lf\n",pi * r * r);

    return 0;
}
#endif
